1. Field of the Invention
The present invention relates to a centering mechanism, centering unit, semiconductor manufacturing apparatus, and centering method, and more specifically, to a centering mechanism for securely delivering objects to be processed between an automated transportation device and a semiconductor manufacturing apparatus, a centering unit provided with the centering mechanism, a semiconductor manufacturing apparatus, and a centering method.
2. Description of the Related Art
In an inspection process of a semiconductor manufacturing apparatus, for example, probers are used as testing units for integrated circuits (hereinafter referred to as “devices”) that are formed on a semiconductor wafer (hereinafter referred to simply as “wafer”). Usually, a prober comprises a loader chamber and a prober chamber. The loader chamber includes a stage portion, wafer transportation mechanism, and pre-alignment mechanism. The stage portion carries thereon a carrier that is stored with a plurality of wafers (e.g., 25 wafers). The wafer transportation mechanism (hereinafter referred to as “arm mechanism”) transports the wafers one after another from the carrier stage portion. The pre-alignment mechanism (hereinafter referred to as “sub-chuck”) pre-aligns the wafers transported by means of the arm mechanism.
The prober chamber is a section for testing the devices on the wafer for electrical properties. The prober chamber is provided with a step (hereinafter referred to as “main chuck”), alignment mechanism, probe card, and test head. The main chuck carries the wafer thereon and moves in X-, Y-, Z-, and θ-directions. The alignment mechanism, in conjunction with the main chuck, aligns the wafer with respect to the probe card. The probe card is located over the main chuck. The test head is located between the probe card and a tester and electrically connects the two.
In testing the devices on the wafer for electrical properties, an operator places the carrier, which is stored with a plurality of wafers in a lot, on the carrier stage portion of the loader chamber. When the prober is actuated, the arm mechanism takes out the wafers in the carrier one after another, the pre-alignment mechanism pre-aligns the wafers, and the arm mechanism delivers the wafers onto the main chuck in the prober chamber.
In the loader chamber, the main chuck and the alignment mechanism align the wafers. The main chuck indexes the aligned wafers. Every time each wafer is indexed, probes of the probe card come electrically into contact with electrodes of the devices on the wafer, whereupon the tester tests the devices for predetermined electrical properties. After the checkup, the arm mechanism of the loader chamber receives the wafer on the main chuck and restores it to its original position in the carrier. The next wafer is checked up by repeating these steps of operation. When the inspection of all the wafers in the carrier is finished, the operator replaces the carrier with another carrier, whereupon devices on each wafer in the new carrier are checked for electrical properties.
If the diameter of each wafer is 300 mm or more, for example, the carrier that stores a plurality of wafers is so heavy that the operator can hardly carry the carrier around, which could be dangerous. This problem is not limited to probers, and is common to semiconductor manufacturing apparatuses and other apparatuses that process wafer-type substrates.
Proposed in Jpn. Pat. Appln. KOKAI Publication No. 10-303270 is a method of transportation in which an automated transportation vehicle (hereinafter referred to as “AGV”) transports carriers so that wafers of the same lot can be delivered in each carrier between the AGV and equipment in each process or stage.
If the wafers have large diameters or advanced hyperfine structures, processing each wafer takes longer. Thus, according to the method for processing the wafers in each carrier, the processed wafers are inevitably detained in the apparatus for a long period of time, which lowers the production efficiency. Accordingly, a single wafer processing system is proposed such that the semiconductor manufacturing apparatus processes the wafers that are delivered one after another between itself and the automated transportation vehicle. This single wafer processing system can increase the production efficiency. If the positional accuracy of the delivery of the wafers between the automated transportation vehicle and the semiconductor manufacturing apparatus is poor, according to this system, however, the wafers cannot be delivered accurately. The single wafer processing system requires construction of a general-purpose automated transportation system that can handle wafers of different diameters at the same time.